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docs: networking: convert ppp_generic.txt to ReST
- add SPDX header; - adjust title markup; - mark code blocks and literals as such; - mark tables as such; - adjust identation, whitespaces and blank lines where needed; - add to networking/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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Mauro Carvalho Chehab
David S. Miller
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32c01266c0
commit
71120802eb
@ -93,6 +93,7 @@ Contents:
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phonet
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pktgen
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plip
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ppp_generic
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.. only:: subproject and html
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@ -1,8 +1,12 @@
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PPP Generic Driver and Channel Interface
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----------------------------------------
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.. SPDX-License-Identifier: GPL-2.0
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Paul Mackerras
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========================================
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PPP Generic Driver and Channel Interface
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========================================
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Paul Mackerras
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paulus@samba.org
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7 Feb 2002
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The generic PPP driver in linux-2.4 provides an implementation of the
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@ -19,7 +23,7 @@ functionality which is of use in any PPP implementation, including:
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* simple packet filtering
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For sending and receiving PPP frames, the generic PPP driver calls on
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the services of PPP `channels'. A PPP channel encapsulates a
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the services of PPP ``channels``. A PPP channel encapsulates a
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mechanism for transporting PPP frames from one machine to another. A
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PPP channel implementation can be arbitrarily complex internally but
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has a very simple interface with the generic PPP code: it merely has
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@ -102,7 +106,7 @@ communications medium and prepare it to do PPP. For example, with an
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async tty, this can involve setting the tty speed and modes, issuing
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modem commands, and then going through some sort of dialog with the
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remote system to invoke PPP service there. We refer to this process
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as `discovery'. Then the user-level process tells the medium to
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as ``discovery``. Then the user-level process tells the medium to
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become a PPP channel and register itself with the generic PPP layer.
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The channel then has to report the channel number assigned to it back
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to the user-level process. From that point, the PPP negotiation code
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@ -111,8 +115,8 @@ negotiation, accessing the channel through the /dev/ppp interface.
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At the interface to the PPP generic layer, PPP frames are stored in
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skbuff structures and start with the two-byte PPP protocol number.
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The frame does *not* include the 0xff `address' byte or the 0x03
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`control' byte that are optionally used in async PPP. Nor is there
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The frame does *not* include the 0xff ``address`` byte or the 0x03
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``control`` byte that are optionally used in async PPP. Nor is there
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any escaping of control characters, nor are there any FCS or framing
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characters included. That is all the responsibility of the channel
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code, if it is needed for the particular medium. That is, the skbuffs
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@ -121,16 +125,16 @@ protocol number and the data, and the skbuffs presented to ppp_input()
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must be in the same format.
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The channel must provide an instance of a ppp_channel struct to
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represent the channel. The channel is free to use the `private' field
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however it wishes. The channel should initialize the `mtu' and
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`hdrlen' fields before calling ppp_register_channel() and not change
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them until after ppp_unregister_channel() returns. The `mtu' field
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represent the channel. The channel is free to use the ``private`` field
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however it wishes. The channel should initialize the ``mtu`` and
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``hdrlen`` fields before calling ppp_register_channel() and not change
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them until after ppp_unregister_channel() returns. The ``mtu`` field
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represents the maximum size of the data part of the PPP frames, that
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is, it does not include the 2-byte protocol number.
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If the channel needs some headroom in the skbuffs presented to it for
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transmission (i.e., some space free in the skbuff data area before the
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start of the PPP frame), it should set the `hdrlen' field of the
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start of the PPP frame), it should set the ``hdrlen`` field of the
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ppp_channel struct to the amount of headroom required. The generic
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PPP layer will attempt to provide that much headroom but the channel
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should still check if there is sufficient headroom and copy the skbuff
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@ -322,6 +326,8 @@ an interface unit are:
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interface. The argument should be a pointer to an int containing
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the new flags value. The bits in the flags value that can be set
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are:
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================ ========================================
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SC_COMP_TCP enable transmit TCP header compression
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SC_NO_TCP_CCID disable connection-id compression for
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TCP header compression
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@ -335,6 +341,7 @@ an interface unit are:
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SC_MP_SHORTSEQ expect short multilink sequence
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numbers on received multilink fragments
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SC_MP_XSHORTSEQ transmit short multilink sequence nos.
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================ ========================================
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The values of these flags are defined in <linux/ppp-ioctl.h>. Note
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that the values of the SC_MULTILINK, SC_MP_SHORTSEQ and
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@ -345,17 +352,20 @@ an interface unit are:
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interface unit. The argument should point to an int where the ioctl
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will store the flags value. As well as the values listed above for
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PPPIOCSFLAGS, the following bits may be set in the returned value:
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================ =========================================
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SC_COMP_RUN CCP compressor is running
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SC_DECOMP_RUN CCP decompressor is running
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SC_DC_ERROR CCP decompressor detected non-fatal error
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SC_DC_FERROR CCP decompressor detected fatal error
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================ =========================================
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* PPPIOCSCOMPRESS sets the parameters for packet compression or
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decompression. The argument should point to a ppp_option_data
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structure (defined in <linux/ppp-ioctl.h>), which contains a
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pointer/length pair which should describe a block of memory
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containing a CCP option specifying a compression method and its
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parameters. The ppp_option_data struct also contains a `transmit'
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parameters. The ppp_option_data struct also contains a ``transmit``
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field. If this is 0, the ioctl will affect the receive path,
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otherwise the transmit path.
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@ -377,7 +387,7 @@ an interface unit are:
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ppp_idle structure (defined in <linux/ppp_defs.h>). If the
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CONFIG_PPP_FILTER option is enabled, the set of packets which reset
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the transmit and receive idle timers is restricted to those which
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pass the `active' packet filter.
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pass the ``active`` packet filter.
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Two versions of this command exist, to deal with user space
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expecting times as either 32-bit or 64-bit time_t seconds.
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@ -391,31 +401,33 @@ an interface unit are:
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* PPPIOCSNPMODE sets the network-protocol mode for a given network
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protocol. The argument should point to an npioctl struct (defined
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in <linux/ppp-ioctl.h>). The `protocol' field gives the PPP protocol
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number for the protocol to be affected, and the `mode' field
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in <linux/ppp-ioctl.h>). The ``protocol`` field gives the PPP protocol
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number for the protocol to be affected, and the ``mode`` field
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specifies what to do with packets for that protocol:
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============= ==============================================
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NPMODE_PASS normal operation, transmit and receive packets
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NPMODE_DROP silently drop packets for this protocol
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NPMODE_ERROR drop packets and return an error on transmit
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NPMODE_QUEUE queue up packets for transmit, drop received
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packets
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============= ==============================================
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At present NPMODE_ERROR and NPMODE_QUEUE have the same effect as
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NPMODE_DROP.
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* PPPIOCGNPMODE returns the network-protocol mode for a given
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protocol. The argument should point to an npioctl struct with the
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`protocol' field set to the PPP protocol number for the protocol of
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interest. On return the `mode' field will be set to the network-
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``protocol`` field set to the PPP protocol number for the protocol of
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interest. On return the ``mode`` field will be set to the network-
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protocol mode for that protocol.
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* PPPIOCSPASS and PPPIOCSACTIVE set the `pass' and `active' packet
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* PPPIOCSPASS and PPPIOCSACTIVE set the ``pass`` and ``active`` packet
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filters. These ioctls are only available if the CONFIG_PPP_FILTER
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option is selected. The argument should point to a sock_fprog
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structure (defined in <linux/filter.h>) containing the compiled BPF
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instructions for the filter. Packets are dropped if they fail the
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`pass' filter; otherwise, if they fail the `active' filter they are
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``pass`` filter; otherwise, if they fail the ``active`` filter they are
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passed but they do not reset the transmit or receive idle timer.
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* PPPIOCSMRRU enables or disables multilink processing for received
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